DEFINITIONS OF OUTSIDE AREAS

Bund Wall Defined
A lined wall around oil tanks designed to catch all oil that leaks from it.   It therefore should have the capacity to retain the volume of oil held within the oil tank and also be oil tight. 

Back Siphonage Defined
The sucking back of dirty water from within a building leading to backflow into a water main if its pressure drops.   All water authorities have regulations to prevent this pollution of the main, eg. by having an air gap under the draw-off taps of sinks or drinking fountains, or ballvalves of cisterns.   A ballvalve with a silencing pipe must have an anti-siphon hole

Benching Defined
Concrete in the base of an inspection chamber, cast to form a deep channel sloping gently up to the walls each side.   It ensures that no solids are left after flooding and is stood on when rodding.

Manholes Defined
As part of the current Building Regulations, you are required to have a manhole (or in some instances a rodding eye is allowed) at each change of direction of the drains or where new drains join an existing run.

Rodding Eye Defined
This is a small access hatch that is used for rodding the drains should they block.